went to have 2 new rear tyres yesterday because they were worn on the inside edge anyway found out the rear trailing arm bushes are kaputt , can these be bought seperate or do i have to buy the complete trailing arm ? any links to where i could buy them would be appreciated

do i have to buy the complete bracket or can i buy the bushes RealOEM.com BMW R53 Cooper S Rr axle support, wheel susp.,whl bearing (http://www.realoem.com/bmw/showparts.do?model=RE32&mospid=48020&btnr=33_1081&hg=33&fg=30)